An important obstacle in the design of video teleconferencing equipment is overcoming the problem of parallax. Parallax arises when the camera and display of a video teleconferencing system do not have a common optic axis. Without this common optic axis, there is a lack of eye contact between the conferee and the associated camera, thus creating a perception of disinterest or preoccupation on the part of the conferee.
Several teleconferencing display terminals have been proposed to overcome the problem of parallax. One solution to the problem involved positioning a camera behind a display screen that is capable of operating in two modes. The display screen is controlled to switch from the first or image display mode to the second or substantially transparent mode. In the first mode the screen displays images from video memory. In the second mode, the camera is controlled to record images appearing on the viewing side of the substantially transparent screen. Compactness results from the use of a flat panel display, such as a liquid crystal display.
While the system described above overcomes the parallax problem, the resulting image quality is poor because light received by the camera is greatly attenuated by the display screen. Moreover, the teleconferencing market will likely insist upon color display screens. The problem is further complicated in the case of color displays because of the large attenuation caused by color filters integrally formed in the display screen.